Strange but true

Why are clouds
white or gray?

More facts

If
you've read Why is the sky blue?
you'll know that there is actually nothing blue in the sky - we
just see it this colour because blue light from the sun is reflected
into our eyes by air molecules. Clouds, however, are made up of
water or ice droplets and these interact with light differently
than air molecules. As the white light from the sun shines on the
cloud, the water droplets scatter it in all directions. Because
all the colors making up light are scattered, we should see the
cloud as white.

But rain clouds tend to be gray, what's this all about? Firstly,
it rains when water and ice droplets in the cloud get too big
to be held up by the rising air. Clouds containing all this water
can get pretty big and thick. When a cloud gets to about 3000
feet thick, it will not allow any light through and this is what
happens with gray clouds. So the sun will be shining on the tops
of the clouds, making them look white if you happen to be in a
plane but won't reach the bottoms, so the clouds look gray to
us on the ground. It also depends on where you are standing -
if you're right under the cloud its going to look pretty dark
but as it moves away, the side is illuminated by the sun and it
will look white.

Also, storms often happen in the late afternoon when the sun
is no longer right above us. This means that clouds will have
a good chance of getting between us and the sun so we won't get
much light and the cloud will look darker. Clouds can even look
black - this happens with tornados. These clouds are so big and
dense that they block out all light from the sun.

Disclaimer!
This web site is for entertainment purposes and
while every effort is made to be scientifically correct, some of
the facts here may be heavily simplified or not completely accurate
(although we do try our best!). As with everything you read on the
net, check a variety of sources before quoting something in homework.
If you think we've got something wrong, by all means leave a comment
for other visitors to read.